These days, the prices of digital still cameras continue to drop. One reason for this is that the chip size of a solid state image sensor is becoming small. As the chip size of the solid state image sensor decreases, an image sensing unit including a photographing optical system becomes small. For further downsizing, the photographing optical system itself is made compact. In order to downsize the photographing optical system, the exit pupil of the photographing optical system must be arranged close to the solid state image sensor. As a result, the inclination angle (incident angle), to the optical axis, of light incident on the periphery of the input portion of the solid state image sensor becomes large. A large incident angle of light incident on the solid state image sensor inhibits light from reaching a photo-electric converting portion.
To prevent this problem, for example, in a solid state image capturing apparatus disclosed in Japanese Patent Laid-Open No. 11-274443, a planoconvex lens is interposed between the on-chip microlens and photo-electric converting portion of the solid state image capturing apparatus so as to be convex on the side of the photo-electric converting portion. This structure can increase the light intake efficiency at a wide light incident angle even in a solid state image capturing apparatus having a small-area photo-electric converting portion.
Japanese Patent Laid-Open No. 2000-164839 discloses a solid state image capturing apparatus in which a convex lens is arranged immediately above the photo-electric converting portion.
However, in the solid state image capturing apparatus disclosed in Japanese Patent Laid-Open No. 11-274443, the planoconvex lens interposed between the on-chip microlens and the photo-electric converting portion is convex on the side of the photo-electric converting portion. Part of light reaching at a large incident angle is totally reflected by the convex lens portion, and light cannot be effectively guided to the photo-electric converting portion.
As one method of preventing total reflection by the convex lens portion, a planoconvex lens 40 which is convex on the side of an on-chip microlens 25 is interposed between the on-chip microlens 25 and a photo-electric converting portion 11, as shown in FIG. 9 which is a sectional view showing a solid state image sensor 200. If the planoconvex lens 40 is formed after a metal electrode layer 31 and protective layer 41 are formed, it projects from the protective layer 41 toward the on-chip microlens 25. The distance between the on-chip microlens 25 and the planoconvex lens 40 becomes long, increasing the distance between the on-chip microlens 25 and the photo-electric converting portion 11. It becomes difficult to guide light at a large incident angle to the photo-electric converting portion 11.
In the solid state image capturing apparatus disclosed in Japanese Patent Laid-Open No. 2000-164839, the convex lens is formed immediately above the photo-electric converting portion, i.e., near the photo-electric converting portion. The convex lens hardly contributes to condensing light incident on the photo-electric converting portion.